Metformin alleviates LPS-induced inflammation via suppression of the MAPK/AP-1 pathway in human dental pulp cells
DOI:
https://doi.org/10.1590/1678-7765-2026-0493Keywords:
AP-1, Inflammation, LPS, MAPK pathway, MetforminAbstract
Objective Metformin, a first-line antidiabetic drug, has been increasingly recognized for its anti-inflammatory actions beyond glycemic control. This study investigated whether metformin modulates lipopolysaccharide (LPS)-induced inflammatory responses in human dental pulp cells (HDPCs) and explored the underlying signaling mechanisms. Methodology In HDPCs stimulated with Escherichia coli LPS in the presence or absence of metformin, cell viability, inflammatory mediator expression, mitogen-activated protein kinase (MAPK)/activator protein-1 (AP-1) signaling, and autophagy-related LC3 conversion were examined. Results Metformin and LPS treatment did not significantly affect HDPC viability at the tested concentrations. LPS stimulation increased the expression of pro-inflammatory mediators, including interleukin-6 and cyclooxygenase-2, whereas metformin significantly attenuated these responses. Mechanistically, metformin suppressed LPS-induced phosphorylation of p38, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and AP-1. Pharmacological inhibition of MAPK signaling also reduced AP-1 phosphorylation and interleukin-6 expression in LPS-stimulated HDPCs, supporting the involvement of MAPK-dependent AP-1 activation in the inflammatory response. Additionally, LPS enhanced LC3-I to LC3-II conversion, whereas metformin attenuated this autophagy-associated response. Conclusion These findings suggest that metformin attenuates LPS-induced inflammatory responses in HDPCs, at least in part, by suppressing MAPK/AP-1 signaling and modulating autophagy-associated signaling. Metformin may therefore have biological relevance as a host-modulatory agent in pulpal inflammation.
Downloads
References
1- Eubanks EJ, Tarle SA, Kaigler D. Tooth storage, dental pulp stem cell isolation, and clinical scale expansion without animal serum. J Endod. 2014;40(5):652-7. doi: 10.1016/j.joen.2014.01.005
» https://doi.org/10.1016/j.joen.2014.01.005
2- Warfvinge J, Dahlén G, Bergenholtz G. Dental pulp response to bacterial cell wall material. J Dent Res. 1985;64(8):1046-50. doi: 10.1177/00220345850640080401
3- Siqueira JF Jr, Rôças IN, Silva MG. Prevalence and clonal analysis of Porphyromonas gingivalis in primary endodontic infections. J Endod. 2008;34(11):1332-6. doi: 10.1016/j.joen.2008.08.021
» https://doi.org/10.1016/j.joen.2008.08.021
4- Chen J, Xu H, Xia K, Cheng S, Zhang Q. Resolvin E1 accelerates pulp repair by regulating inflammation and stimulating dentin regeneration in dental pulp stem cells. Stem Cell Res Ther. 2021;12(1):75. doi: 10.1186/s13287-021-02141-y
» https://doi.org/10.1186/s13287-021-02141-y
5- Nam OH, Kim JH, Kang SW, Chae YK, Jih MK, You HH, et al. Ginsenoside Rb1 alleviates lipopolysaccharide-induced inflammation in human dental pulp cells via the PI3K/Akt, NF-?B, and MAPK signalling pathways. Int Endod J. 2024;57(6):759-68. doi: 10.1111/iej.14058
» https://doi.org/10.1111/iej.14058
6- Sabeti MA, Nikghalb KD, Pakzad R, Fouad AF. Expression of selected inflammatory mediators with different clinical characteristics of pulpal inflammation. J Endod. 2024;50(3):336-43. doi: 10.1016/j.joen.2023.11.016
» https://doi.org/10.1016/j.joen.2023.11.016
7- Nakanishi T, Shimizu H, Hosokawa Y, Matsuo T. An immunohistological study on cyclooxygenase-2 in human dental pulp. J Endod. 2001;27(6):385-8. doi: 10.1097/00004770-200106000-00003
» https://doi.org/10.1097/00004770-200106000-00003
8- Kang YJ, Wingerd BA, Arakawa T, Smith WL. Cyclooxygenase-2 gene transcription in a macrophage model of inflammation. J Immunol. 2006;177(11):8111-22. doi: 10.4049/jimmunol.177.11.8111
» https://doi.org/10.4049/jimmunol.177.11.8111
9- Luo Y, Zheng SG. Hall of fame among pro-inflammatory cytokines: interleukin-6 gene and its transcriptional regulation mechanisms. Front Immunol. 2016;7:604. doi: 10.3389/fimmu.2016.00604
» https://doi.org/10.3389/fimmu.2016.00604
10- Johnson GL, Lapadat R. Mitogen-activated protein kinase pathways mediated by ERK, JNK, and p38 protein kinases. Science. 2002;298(5600):1911-2. doi: 10.1126/science.1072682
» https://doi.org/10.1126/science.1072682
11- Wu L, Li X, Wu H, Long W, Jiang X, Shen T, et al. 5-Methoxyl aesculetin abrogates lipopolysaccharide-induced inflammation by suppressing MAPK and AP-1 pathways in RAW 264.7 cells. Int J Mol Sci. 2016;17(3):315. doi: 10.3390/ijms17030315
» https://doi.org/10.3390/ijms17030315
12- Whitmarsh AJ, Davis RJ. Transcription factor AP-1 regulation by mitogen-activated protein kinase signal transduction pathways. J Mol Med (Berl). 1996;74(10):589-607. doi: 10.1007/s001090050063
» https://doi.org/10.1007/s001090050063
13- Pulverer BJ, Kyriakis JM, Avruch J, Nikolakaki E, Woodgett JR. Phosphorylation of c-jun mediated by MAP kinases. Nature. 1991;353(6345):670-4. doi: 10.1038/353670a0
» https://doi.org/10.1038/353670a0
14- Min KS, Kim HI, Chang HS, Kim HR, Pae HO, Chung HT, et al. Involvement of mitogen-activated protein kinases and nuclear factor-kappa B activation in nitric oxide-induced interleukin-8 expression in human pulp cells. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;105(5):654-60. doi: 10.1016/j.tripleo.2007.11.011
» https://doi.org/10.1016/j.tripleo.2007.11.011
15- Zhao Y, Wang CL, Li RM, Hui TQ, Su YY, Yuan Q, et al. Wnt5a promotes inflammatory responses via nuclear factor ?B (NF-?B) and mitogen-activated protein kinase (MAPK) pathways in human dental pulp cells. J Biol Chem. 2014;289(30):21028-39. doi: 10.1074/jbc.M113.546523
» https://doi.org/10.1074/jbc.M113.546523
16- He X, Jiang W, Luo Z, Qu T, Wang Z, Liu N, et al. IFN-? regulates human dental pulp stem cells behavior via NF-?B and MAPK signaling. Sci Rep. 2017;7:40681. doi: 10.1038/srep40681
» https://doi.org/10.1038/srep40681
17- Goodarzi MO, Bryer-Ash M. Metformin revisited: re-evaluation of its properties and role in the pharmacopoeia of modern antidiabetic agents. Diabetes Obes Metab. 2005;7(6):654-65. doi: 10.1111/j.1463-1326.2004.00448.x
» https://doi.org/10.1111/j.1463-1326.2004.00448.x
18- Lin H, Ao H, Guo G, Liu M. The role and mechanism of metformin in inflammatory diseases. J Inflamm Res. 2023;16:5545-64. doi: 10.2147/JIR.S436147
» https://doi.org/10.2147/JIR.S436147
19- Takemura Y, Osuga Y, Yoshino O, Hasegawa A, Hirata T, Hirota Y, et al. Metformin suppresses interleukin (IL)-1ß-induced IL-8 production, aromatase activation, and proliferation of endometriotic stromal cells. J Clin Endocrinol Metab. 2007;92(8):3213-8. doi: 10.1210/jc.2006-2486
» https://doi.org/10.1210/jc.2006-2486
20- Nath N, Khan M, Paintlia MK, Singh I, Hoda MN, Giri S. Metformin attenuated the autoimmune disease of the central nervous system in animal models of multiple sclerosis. J Immunol. 2009;182(12):8005-14. doi: 10.4049/jimmunol.0803563
» https://doi.org/10.4049/jimmunol.0803563
21- Wang HW, Lai EH, Yang CN, Lin SK, Hong CY, Yang H, et al. Intracanal metformin promotes healing of apical periodontitis via suppressing inducible nitric oxide synthase expression and monocyte recruitment. J Endod. 2020;46(1):65-73. doi: 10.1016/j.joen.2019.10.001
» https://doi.org/10.1016/j.joen.2019.10.001
22- Hong CY, Lin SK, Wang HW, Shun CT, Yang CN, Lai EH, et al. Metformin reduces bone resorption in apical periodontitis through regulation of osteoblast and osteoclast differentiation. J Endod. 2023;49(9):1129-37. doi: 10.1016/j.joen.2023.07.005
» https://doi.org/10.1016/j.joen.2023.07.005
23- Pradeep AR, Patnaik K, Nagpal K, Karvekar S, Ramamurthy BL, Naik SB, et al. Efficacy of locally-delivered 1% metformin gel in the treatment of intrabony defects in patients with chronic periodontitis: a randomized, controlled clinical trial. J Investig Clin Dent. 2016;7(3):239-45. doi: 10.1111/jicd.12150
» https://doi.org/10.1111/jicd.12150
24- Tan Y, Chen J, Jiang Y, Chen X, Li J, Chen B, et al. The anti-periodontitis action of metformin via targeting NLRP3 inflammasome. Arch Oral Biol. 2020;114:104692. doi: 10.1016/j.archoralbio.2020.104692
» https://doi.org/10.1016/j.archoralbio.2020.104692
25- Chang J, Zhang C, Tani-Ishii N, Shi S, Wang CY. NF-?B activation in human dental pulp stem cells by TNF and LPS. J Dent Res. 2005;84(11):994-8. doi: 10.1177/154405910508401105
» https://doi.org/10.1177/154405910508401105
26- Farges JC, Alliot-Licht B, Renard E, Ducret M, Gaudin A, Smith AJ, et al. Dental pulp defence and repair mechanisms in dental caries. Mediators Inflamm. 2015;2015:230251. doi: 10.1155/2015/230251
» https://doi.org/10.1155/2015/230251
27- Bindal P, Ramasamy TS, Kasim NH, Gnanasegaran N, Chai WL. Immune responses of human dental pulp stem cells in lipopolysaccharide-induced microenvironment. Cell Biol Int. 2018;42(7):832-40. doi: 10.1002/cbin.10938
» https://doi.org/10.1002/cbin.10938
28- Vasamsetti SB, Karnewar S, Kanugula AK, Thatipalli AR, Kumar JM, Kotamraju S. Metformin inhibits monocyte-to-macrophage differentiation via AMPK-mediated inhibition of STAT3 activation: potential role in atherosclerosis. Diabetes. 2015;64(6):2028-41. doi: 10.2337/db14-1225
» https://doi.org/10.2337/db14-1225
29- Cameron AR, Morrison VL, Levin D, Mohan M, Forteath C, Beall C, et al. Anti-inflammatory effects of metformin irrespective of diabetes status. Circ Res. 2016;119(5):652-65. doi: 10.1161/CIRCRESAHA.116.308445
» https://doi.org/10.1161/CIRCRESAHA.116.308445
30- Zha QB, Wei HX, Li CG, Liang YD, Xu LH, Bai WJ, et al. ATP-induced inflammasome activation and pyroptosis is regulated by AMP-activated protein kinase in macrophages. Front Immunol. 2016;7:597. doi: 10.3389/fimmu.2016.00597
» https://doi.org/10.3389/fimmu.2016.00597
31- Craig EA, Stevens MV, Vaillancourt RR, Camenisch TD. MAP3Ks as central regulators of cell fate during development. Dev Dyn. 2008;237(11):3102-14. doi: 10.1002/dvdy.21750
» https://doi.org/10.1002/dvdy.21750
32- Lee JC, Yu MK, Lee R, Lee YH, Jeon JG, Lee MH, et al. Terrein reduces pulpal inflammation in human dental pulp cells. J Endod. 2008;34(4):433-7. doi: 10.1016/j.joen.2008.01.015
» https://doi.org/10.1016/j.joen.2008.01.015
33- Yoon WJ, Moon JY, Song G, Lee YK, Han MS, Lee JS, et al. Artemisia fukudo essential oil attenuates LPS-induced inflammation by suppressing NF-?B and MAPK activation in RAW 264.7 macrophages. Food Chem Toxicol. 2010;48(5):1222-9. doi: 10.1016/j.fct.2010.02.014
» https://doi.org/10.1016/j.fct.2010.02.014
34- Xu X, Kwon OK, Shin IS, Mali JR, Harmalkar DS, Lim Y, et al. Novel benzofuran derivative DK-1014 attenuates lung inflammation via blocking of MAPK/AP-1 and AKT/mTOR signaling in vitro and in vivo. Sci Rep. 2019;9(1):862. doi: 10.1038/s41598-018-36925-9
» https://doi.org/10.1038/s41598-018-36925-9
35- Alam MB, Chowdhury NS, Sohrab MH, Rana MS, Hasan CM, Lee SH. Cerevisterol alleviates inflammation via suppression of MAPK/NF-?B/AP-1 and activation of the Nrf2/HO-1 signaling cascade. Biomolecules. 2020;10(2):199. doi: 10.3390/biom10020199
» https://doi.org/10.3390/biom10020199
36- Li X, Xu M, Shen J, Li Y, Lin S, Zhu M, et al. Sorafenib inhibits LPS-induced inflammation by regulating Lyn-MAPK-NF-kB/AP-1 pathway and TLR4 expression. Cell Death Discov. 2022;8(1):281. doi: 10.1038/s41420-022-01073-7
» https://doi.org/10.1038/s41420-022-01073-7
37- Feng X, Chen W, Ni X, Little PJ, Xu S, Tang L, et al. Metformin, macrophage dysfunction and atherosclerosis. Front Immunol. 2021;12:682853. doi: 10.3389/fimmu.2021.682853
» https://doi.org/10.3389/fimmu.2021.682853
38- Jin Q, Cheng J, Liu Y, Wu J, Wang X, Wei S, et al. Improvement of functional recovery by chronic metformin treatment is associated with enhanced alternative activation of microglia/macrophages and increased angiogenesis and neurogenesis following experimental stroke. Brain Behav Immun. 2014;40:131-42. doi: 10.1016/j.bbi.2014.03.003
» https://doi.org/10.1016/j.bbi.2014.03.003
39- Collier CA, Bruce CR, Smith AC, Lopaschuk G, Dyck DJ. Metformin counters the insulin-induced suppression of fatty acid oxidation and stimulation of triacylglycerol storage in rodent skeletal muscle. Am J Physiol Endocrinol Metab. 2006;291(1):E182-9. doi: 10.1152/ajpendo.00272.2005
» https://doi.org/10.1152/ajpendo.00272.2005
40- Qi T, Chen Y, Li H, Pei Y, Woo SL, Guo X, et al. A role for PFKFB3/iPFK2 in metformin suppression of adipocyte inflammatory responses. J Mol Endocrinol. 2017;59(1):49-59. doi: 10.1530/JME-17-0066
» https://doi.org/10.1530/JME-17-0066
41- Zheng J, Woo SL, Hu X, Botchlett R, Chen L, Huo Y, et al. Metformin and metabolic diseases: a focus on hepatic aspects. Front Med. 2015;9(2):173-86. doi: 10.1007/s11684-015-0384-0
» https://doi.org/10.1007/s11684-015-0384-0
42- Rajeev D, MacIver NJ. Metformin as a therapeutic agent for obesity-associated immune dysfunction. J Nutr. 2024;154(8):2534-42. doi: 10.1016/j.tjnut.2024.07.001
» https://doi.org/10.1016/j.tjnut.2024.07.001
43- Moiseeva O, Deschênes-Simard X, St-Germain E, Igelmann S, Huot G, Cadar AE, et al. Metformin inhibits the senescence-associated secretory phenotype by interfering with IKK/NF-?B activation. Aging Cell. 2013;12(3):489-98. doi: 10.1111/acel.12075
» https://doi.org/10.1111/acel.12075
44- Taha RR, El-Khazragy N, Ibrahim SH, Hassan N. Dose-dependent effects of metformin on proliferation and odontogenic differentiation of dental pulp stem cells. BMC Oral Health. 2026;26(1):771. doi: 10.1186/s12903-026-08221-w
» https://doi.org/10.1186/s12903-026-08221-w
45- Qin W, Chen JY, Guo J, Ma T, Weir MD, Guo D, et al. Novel calcium phosphate cement with metformin-loaded chitosan for odontogenic differentiation of human dental pulp cells. Stem Cells Int. 2018;2018:7173481. doi: 10.1155/2018/7173481
46- Pan Q, Lu X, Zhao C, Liao S, Chen X, Guo F, et al. Metformin: the updated protective property in kidney disease. Aging (Albany NY). 2020;12(9):8742-59. doi: 10.18632/aging.103095
Downloads
Published
Issue
Section
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Todo o conteúdo do periódico, exceto onde está identificado, está licenciado sob uma Licença Creative Commons do tipo atribuição CC-BY.
